Discovery of a young massive stellar cluster near HESS J1813-178

TL;DR

A young stellar cluster near HESS J1813-178 was discovered in the Galactic disk, with spectroscopic analysis revealing its age, mass, and stellar composition, and its association with supernova remnants and high-energy sources.

Contribution

This paper reports the first identification and characterization of a young stellar cluster near HESS J1813-178 using spectroscopic data, linking it to high-energy phenomena.

Findings

Cluster age of 6-8 million years

Initial mass of approximately 2000 solar masses

Association with supernova remnants and high-energy sources

Abstract

We present the serendipitous discovery of a young stellar cluster in the Galactic disk at l=12deg. Using Keck/NIRSPEC, we obtained high- and low-resolution spectroscopy of several stars in the cluster, and we identified one red supergiant and two blue supergiants. The radial velocity of the red supergiant provides a kinematic cluster distance of 4.7pm0.4 kpc, implying luminosities of the stars consistent with their spectral types. Together with the known Wolf-Rayet star located 2.4' from the cluster center, the presence of the red supergiant and the blue supergiants suggests a cluster age of 6-8 Myr, and an initial mass of 2000 Msun. Several stars in the cluster are coincident with X-ray sources, including the blue supergiants and the Wolf-Rayet star. This is indicative of a high binary fraction, and is reminiscent of the massive young cluster Westerlund 1. The cluster is coincident with two supernova remnants, SNR G12.72-0.0 and G12.82-0.02, and the highly magnetized pulsar associated with the TeV gamma-ray source HESS J1813-178. The mixture of spectral types suggests that the progenitors of these objects had initial masses of 20 - 30 Msun.